- What is URL percent-encoding and how does it work?
- Percent-encoding (defined in RFC 3986) replaces characters that are unsafe or reserved in URLs with a percent sign followed by two hexadecimal digits representing the character's byte value. For example, a space becomes %20, an ampersand becomes %26, and a question mark becomes %3F. This ensures URLs remain valid and parseable across all browsers, servers, and network infrastructure.
- What is the difference between encodeURIComponent and encodeURI in JavaScript?
- encodeURIComponent() encodes all characters except unreserved characters (A-Z, a-z, 0-9, -, _, ., ~), making it ideal for encoding individual query parameter values. encodeURI() preserves URL structural characters like ://?#[]@!$&'()*+,;= and only encodes characters that are completely invalid in URLs. This tool follows encodeURIComponent() behavior for maximum encoding safety.
- Why does a space encode as %20 sometimes and + other times?
- In standard URL percent-encoding (RFC 3986), spaces encode as %20. In application/x-www-form-urlencoded format (used by HTML form submissions), spaces encode as +. Most modern APIs and JavaScript's encodeURIComponent() use %20. If you see + in URLs, it's typically from form-encoded data or legacy systems.
- What is double URL encoding and how do I fix %2520 errors?
- Double encoding occurs when an already-encoded string is encoded again. For example, a space (%20) gets re-encoded to %2520 because the % sign itself is encoded to %25. To fix this, decode the string once to get the single-encoded form, identify where the duplicate encoding occurs in your code pipeline, and ensure encoding happens only once at the output boundary.
- How do I encode Unicode and special characters in URLs?
- Unicode characters are first converted to their UTF-8 byte representation, then each byte is percent-encoded. For example, the euro sign is encoded as %E2%82%AC (three UTF-8 bytes). This tool handles all Unicode characters automatically, producing correct multi-byte percent-encoded sequences.
- Can I use this tool to encode UTM parameters and campaign tracking URLs?
- Yes. Encode individual UTM parameter values (utm_source, utm_medium, utm_campaign, utm_content, utm_term) that contain spaces, ampersands, or special characters before appending them to your tracking URL. This prevents broken analytics attribution and ensures Google Analytics, Adobe Analytics, and other platforms correctly parse your campaign data.
- Is this URL encoder decoder free and is my data stored?
- Yes, completely free with no signup required. All encoding and decoding runs 100% client-side in your browser — your URLs, query strings, and data are never uploaded to any server or stored anywhere.
